Why hasn't Boeing or Airbus installed a video camera below in cargo to identify smoke visually, near the ducts? Surely there must be a way to get around these false alarms that are becoming a major issue!!
Was attempted but blocked by baggage handler unions in the US, seen as an invasion of privacy. Don't know why they didn't make it an airborne system.
I guess it all comes down to money. Any system you put on an aircraft needs to be operational, otherwise it needs to be on the MEL. Airline's see it as an extra costs and would therefore fight it at all costs.
This probably happens rarely enough that the costs of the occasional diversion do not outweigh the modification and maintenance costs to have cameras in the hold.